Gasket material



Patented Aug. 7, 1 945 Roger C. Balm-Port Clinton, Ohio,

The Standard Products m Mich, a corporation of Ohio asslgnorto Detroit.

No Drawing. Application September 2:, 1m, SerialNc. 459,43: I

The invention relates to a novel and improved synthetic composition for use, for example; in the manufacture of gaskets. It particularly relates to a composition of'this nature containing Y substantial amounts of wood flour and of an oil resistant butadiene copolymer such as butadieneacrylonitrile.

One of the major applications for gaskets is the furnishing of oil-tight and gas-tight seals, for

and swells out or all proportion to its original volume. A gasket nevertheless should be pliableto the extent that it should resiliently yield to deforming forces, but it should have sumcient inherent elasticity to offer a continued resistance to such forces so as to maintain a satisfactory sealing or packing eflfect. Some gasket materials, heretofore available, eventually acquire a "permanent se through deterioration of their elastic characteristics. Other such materials are soluble in hydrocarbon fuels or lubricants, or deteriorate when in contact therewith. Some gasket materials, while satisfactory with respect to their sealing and hydrocarbon resisting characteristics are adversely aflected by atmospheric conditions, particularly humidity, whereby, for example, gasket stock or finished gaskets undergo dimen sional changes or contour distortions while in storage, to such an extent that when taken from storage they cannot be fitted in their intended position. In many cases protective wrappings or treatments have been resorted to in an attempt to prevent climatic attack but of course such expcgmdients. even ii. effective, add to the eventual An object of the present invention is to provide a novel packing material which is not appreciably obvious and will in part become apparent as the description proceeds.

One of the major and necessary constituents of my composition of matter is an oil resistant copolymer of butadiene with acrylonitrile. is a commercially available rubberllke material, identifiable under such trade names as Hycar 0R, Buna N, or 'I'hiokol RD. It is highly resistant to solvent attack or deterioration when in contact with hydrocarbon fluids. It should be present in an amount between about 15% and by weight of the total batch.

Another major and necessary constituent of my gasket material is wood flour. It is readily available commercially and should be finer than 40 mesh. Computed on the weight of the total batch, the wood flour should be present in amount between about 20 per cent and 40 per cent.

I use fromabout 10 per cent to 30 per cent by weight of one of the recognized plasticizing agents such as a petroleum base or coal tar base oil, or an organic compound of the character of octadecine nitrlle, tricresyl phosphate, or a cumarone-indene compound.

It has been observed that such plasticizing gents progressively leach out of gasket material when in constant service contact with hydrocarbon fuels or lubricants To counteract the resulting volumetric contraction, I incorporate in the material a swelling agent, such as a rubberlike material (by which terminology I mean to include natural rubber, either raw or reclaim), in an amount between about 5 per cent and 25 per cent of the weight of the butadiene copolymer, or, when computed on the weight of the total batch, the range would be between 0.! per cent and 11.3 per cent. This latter range gives the minimum and maximum limits as calculated on the total batch, but for satisfactory results the actual amount of natural rubber should preferably be calculated as a proportion of the amount of butadiene copolymer present, as indicated by the earlier range in this paragraph. .As previously indicated, natural cured rubber is affected by hydrocarbon fluids and swells when in contact therewith. The presence of cured rubber in amount as above indicatedcounteracts the shrinkage resulting from the loss of plasticizer and maintains a substantially constant volumetric relationship. However, constant volume is not essential and, if desired, enough cured rubber may be included to eflect a slight increase in volume, so as to accentuate the packing effect.

I preferably also incorporate in the total batch a small proportion of one or more. of the usual I Per cent total hydrocarbon Per cent total batch Benzothiazyl disuliide Sulf ur PhenyLgeta-naphthylamine e ace-ma Zinc ozi s eps:

3. 33 OO'OIOI As in the case of the calculation for the preferred amount of natural rubber, the first percentage column in the above tabulation should be used for determining the preferred range of each curing agent with relation to the total hydrocarbon content, the last column, namel the per cent of the total batch, being included for convenience.

As a filler I may employ from about 15 per cent to 30 per cent of short fibered asbestos, calculated on the total weight of the batch.

The following formula is suggested as one suitable mix for a gasket material, the composition being tabulated both in parts by weight, and in approximate per cent by weight, calculated on the total weight of the mix.

Parts by weight Per cent by wei ht Hycar R The degree of hardness desired in a gasket material is determined by the correlation of a number of factors, including the particular application or use for which the gasket is intended. This in turn determines the compressive force necessary, in conjunction with the area of the gasket available to receive the application of said force. .4

the trade names Hycar OS or Buna S. Thisstyrene copolymer is another suitable rubberlike swelling agent. It is not sufficiently resistant to attack by hydrocarbon fluids to be used as the principal rubberlike synthetic material so as to replace, in whole or in part, the butadiene acrylonitrile copolymer, but its solventresponse to hydrocarbon fluids makes it feasible to substitute said butadiene-styrene copolymer as a swelling agent instead of the natural rubber heretofore suggested, especially in view of the present supply problems arising from limitations on the use of natural rubber.

In compounding the materials the Hyc'ar and reclaimed rubber are fed into a standard rubber mill and are rolled until smooth, which is generally achieved in between 10 and'30 minutes. The accelerator, antioxidant, and zinc oxide are then added. followed by dry powdered asbestos and .wood flour. The plasticizing agent or agents may be added concurrently with the asbestos and wood flour since the oleaginous plasticizing material facilitates the incorporation of the dry ingradients in the mix. The sulfur is usually added last.

The mix is calendered in sheets of about the desired thickness and the gaskets are cut direct ly from this uncured stock. This permits the scrap trimmings to be recalendered in a succeeding batch. The gaskets are vulcanized in an oven at approximately 275 F. for from three to four hours, the air pressure within the vulcanizer being maintained at between 20 and 50 pounds per square inch.

Gaskets made from the novel composition of matter hereinabove disclosed have a high resistance to solvent attack by hydrocarbon fluids and to any deterioration resulting therefrom. Such gaskets are also unafiected by aging or weathering and require no special protective measures or means during storage prior to use.

WhatIclaim is:

1. A composition of matter for use as a packing material, containing from 15 per cent to 45 per cent of an oil resistant butadiene-acrylonitrile copolymer of rubberlike characteristics, from 20 per cent to 40 per cent of wood flour, from 0.25 per cent to 11.25 per cent of natural rubber capable of increasing in volume when in contact with hydrocarbon fluids, and from 10 per cent to 30'per cent of a plasticizerfor said composi tion of matter, said plastiiczer being soluble in hydrocarbon fluids.

2. A composition of matter for use as a packing material containing from 15 per cent to 45 per cent of a butadiene-acrylonitrile copolymer of rubberlike characteristics, from 20 per cent to 40 per cent of wood flour, from 10 per cent to 30 per cent of a plasticizer for said composition of matter, said plasticizer being soluble in hydrocarbon fluids, and from 0.25 per cent to 11.25 per cent of a butadiene styrene copolymer of rubberlike characteristics, and capable of increasing in volume when in contact with hydrocarbon fluids.

3. A composition of matter for use as a packing material, containing from 15 per cent to 45 per cent of an oil resistant butadlene-acrylonitrile copolymer of rubberlike characteristics, from 20 per cent to 40 per cent of wood flour, from 0.25 per cent to 11.25 per cent of natural rubber capable of increasing in volume when in contact with hydrocarbon fluids, and from 10 per cent to 30 per cent of a plasticizer for said composition of matter, said plasticizer being soluble in hydrocarbon fluids, from 15 per cent to 30 per cent of asbestos fiber, and between about 0.75 per cent and 'l per cent of material comprising an antioxidant, a curing agent, and an acccelerating agent.

4. A composition of matter for use as a packing material-containing about 18 per cent of a butadiene-acrylonitrile copolymer of rubberlike char- I Iacterlstics, about 36 per cent of wood flour, about 29 per cent of asbestos fiber, about 2 per cent of natural rubber, about 2 per cent total 0! material comprising a curing reagent. an accelerating agent, and an antioxidant, and about 13 per cent of a plasticizer for said composition of matter, said plasticizer being soluble in hydrocarbon fluids.

5. A composition or matter for use as a packing material, containing from 15 per cent to 45 per cent of an oil resistant butadiene-acrylonitrile copolymer of rubberlike characteristics, from 20 1 per cent to 40 per cent or wood flour, rrom 10 per ROGER C. BASCOM. 

